Over the past 10 years, significant advances have been made in our understanding of acquired myasthenia gravis (MG) in companion animals. The broad spectrum of presenting clinical signs has been defined and an accurate and sensitive diagnostic test is available. Even with these advances, the mortality rate in dogs with acquired MG remains unacceptably high. While an understanding of the genetic basis for susceptibility to autoimmune disease has started to be developed, the trigger for the initiation of this disease is not known and a mechanism for specific suppression of the aberrant immune response against the acetylcholine receptor remains a mystery.